1. Field of the Invention
This invention relates to an orifice plate for an ink jet recording head, a method for producing the orifice plate, and an ink jet recording head provided with the orifice plate.
2. Description of the Prior Art
Non-impact recording methods generate only a small noise which is negligible upon recording so that the methods have recently drawn attentions. Among them, ink jet recording methods (liquid jet recording methods) by which a high speed recording is possible and full color recording can be effected on plain paper without a special treatment, i.e. fixation are very powerful recording methods, and heretofore, various types of ink jet recording methods have been proposed and some of them have been already commercially used while some are now under development.
In such liquid jet recording methods, so-called ink, a recording liquid, is propelled in a form of a droplet and attached to a receiving member to effect recording. The liquid jet recording methods are classified into various types depending upon the method for forming droplets of the recording liquid and the method for controlling the propelling direction of the droplets thus formed.
Among them, U.S. Pat. Nos. 3,683,212, 3,747,120, 3,946,398 etc. disclose liquid jet recording methods, so-called drop-on-demand recording methods, where the recording liquid is ejected and propelled in the form of a droplet through ejection orifices and the droplets are attached to the surface of a receiving member to record. According to said recording methods, the amount of the recording liquid to be ejected is that required for recording only so that it is not necessary to recover any ejected recording liquid not required for recording and provide with any particular means for treating such unnecessarily ejected droplets. In addition, the recording apparatus can be simplified and miniaturized, and it is not necessary to control the propelling direction of droplets of the recording liquid ejected through the ejection orifice. Furthermore, multicolor recording can be easily effected and the like. In view of the foregoing, the recording methods have recently drawn attentions to a great extent.
Japanese Patent Application Laid-open No. 51837/1979, West German Laid-open (DOLS) No. 2843064, U.S. Pat. No. 4,492,966 and U.S. Pat. No. 4,410,899 disclose liquid jet recording methods completely different from the above-mentioned liquid jet recording method in point of the principle as to the formation of droplets to be propelled. However, the liquid jet recording methods disclosed in the above-mentioned patent documents can be not only very effectively applied to the drop-on-demand recording methods, but also can be easily realized in a recording head of multi-orifice type of high density, and therefore, the methods can produce recorded images of high resolution and high quality at a high speed.
The liquid jet recording apparatus used for the drop-on-demand recording method is usually constituted of a recording head having orifices for ejecting a recording liquid in the form of a droplet, liquid flow paths communicating with the respective orifices and having ejection energy generating elements for producing droplets to be propelled and liquid chambers communicating with the liquid flow paths for storing the recording liquid to be supplied to the liquid flow paths, and the recording head being fixed to a carriage capable of scanning relatively over a receiving member.
In the following, referring to the drawing, a conventional method for fabricating orifice plates and the structure of conventional orifice plates will be explained briefly by using steps for fabricating ink jet recording heads.
FIG. 1 is a schematic oblique view of a substrate having ejection energy generating elements of a prior art ink jet recording head. A substrate 6 as a support composed of glass, ceramics, plastics, metal or the like having an ink supplying port 8 is fitted with ejection energy generating elements 7. Electrodes for output of record signal (not shown) are connected with the ejection energy generating elements 7. If necessary, for the purpose of protecting the ejection energy generating elements 7 and the electrodes from electrolytic corrosion caused by contacting the ink, there is provided a protecting layer.
FIG. 2 is a schematic oblique view of the substrate of a prior art ink jet recording head in FIG. 1 additionally provided with liquid flow path walls and an outer frame. In FIG. 2, liquid flow path walls 4 for forming liquid flow paths and an outer frame 5 are mounted on the substrate 6 obtained in FIG. 1.
FIG. 3(a) is a schematic oblique view of an orifice plate having ejecting orifices of a prior art ink jet recording head, and FIG. 3(b) is a schematic cross section taken along the dot-and-dash line in FIG. 3(a).
In FIG. 3(a) and FIG. 3(b), an orifice plate 1 is provided with ejection orifices 2. An adhesive is applied to the outer side regions of orifice plate 1 and then the orifice plate 1 is adhered to substrate 6 obtained in FIG. 2 to complete an ink jet recording head. The completed ink jet recording head is shown in FIG. 4(a) (oblique view) in which 9 denotes the adhesive. FIG. 4(b) is a schematic cross sectional view taken along a dot-and-dash line C-C' in FIG. 4(a). The reference numerals similar to those in FIGS. 1-3 denote the similar parts, respectively.
As a material for the orifice plate 1, there may be generally used metal, glass, ceramics, plastics and the like.
However, according to the above-mentioned prior art method for producing ink jet recording heads, the step for forming liquid flow path walls 4 and outer frame 5 and the step for forming orifice plate 1 are separately carried out so that the number of steps is larger and the number of parts increases. As the result, the cost for production is disadvantageously raised. As a method for forming orifices, there are, for example, the following methods, accompanied with the following drawbacks.
(1) Mechanical processing is liable to cause cracking and form burrs. Therefore, it is difficult to obtain a head of good ejection performance. In order to obtain records of high quality, it is required to make the ejection orifice diameter small, arrange the orifices densely, and make multi-orifices, but these can be attained only to a limited extent when ejection orifices are fabricated by mechanical processing.
(2) When etching is used for fabricating the head, it is desirable to effect etching from both sides of a plate so as to enhance the accuracy of the diameter of the ejection orifice. Therefore, the number of steps increases resulting in high cost.
(3) On an appropriate metal plate is formed a pattern of ejection orifices by using a hardened film of a photosensitive resin, and then, nickel or other metal plating is applied by an electrolytic or a non-electrolytic plating method. The cured film of the photosensitive resin and the metal plate are removed to obtain a plating film having the ejection orifices.
The above-mentioned method has many steps and moreover, it takes a considerably long time in order to obtain the thickness of about 0.1 mm required for necessary strength by means of plating only. As a result, the cost becomes expensive.
For the purpose of eliminating the above-mentioned drawbacks, there have been proposed methods comprising simultaneously integrating liquid flow path walls and orifices. That is, (1) Japanese Patent Application Laid-open No. 118469/1984 discloses a method comprising producing a pattern for forming orifices on a mold having projections and recesses for forming liquid flow path walls and liquid chambers by using a photosensitive resin, applying metal plating to the projections and recesses and patterns for forming orifices, and finally, releasing the plating film from said mold to obtain an orifice plate. The flow sheet of this method is shown in FIG. 5. In addition, (2) there is another method for fabricating an orifice plate comprising integrally shaping orifices, liquid flow path walls and recesses for forming liquid chambers with a resin by using a shaping method such as accurate injection molding, compression molding, transfer molding and the like.
However, the above-mentioned improving methods have the following disadvantages.
The method in (1) above can attain high accuracy, but it requires many steps as shown in FIG. 5 and therefore, the cost can not be so low. In addition, since the metal plating is applied to a considerable thickness, it takes a long time to effect the plating. The waste liquor from the metal plating should be treated so as to avoid possible water pollution. This treatment requires a large capital investment.
The method (2) can provide good mass production as to shaping and therefore, orifice plates of a considerably low cost can be obtained, but the resin shaping can not give orifice plates of a high accuracy (tolerance being several microns or so) and a high density (at least 4 orifices/mm).
In view of the foregoing, inexpensive and highly accurate orifice plates are not available at present.